Insufflation system and method

ABSTRACT

An insufflation system that includes a first tube that inserts into a patient&#39;s airway for providing a primary flow of breathing gas to such a patient. At least one insufflation catheter is provided in or within the first tube for delivering a flow of insufflation gas to the patient. In one embodiment, a flow control system is coupled between the first tube, the insufflation catheter, and a source of insufflation gas to control the flow of gas between the patient circuit, the insufflation catheter, and the source of insufflation gas. In another embodiment, a ventilator and tracheal gas insufflation system are provided in a common housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation-In-Part and claims priorityunder 35 U.S.C. § 120 from U.S. patent application Ser. No. 10/135,260filed Apr. 20, 2003, now U.S. Pat. No. 6,772,382, which is aContinuation of U.S. patent application Ser. No. 09/596,389 filed Jun.16, 2000, now U.S. Pat. No. 6,439,228, which is a Continuation of U.S.patent application Ser. No. 09/453,303, filed Dec. 2, 1999, now U.S.Pat. No. 6,102,042, which claims priority under 35 U.S.C. § 19(e) fromU.S. provisional patent application No. 60/113,222 filed Dec. 22, 1998and 60/138,491 filed Jun. 10, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention pertains to an insufflation system andmethod that delivers a flow of insufflation gas to the airway of apatient to remove expired gases from a patient's anatomical dead spaceand/or the structural dead space in a breathing circuit duringventilation, and, in particular, to an insufflation system and methodthat delivers a flow of insufflation gas to the patient's airway in sucha manner so as to minimize stagnation pressure in the patient's lungsdue to the flow of insufflation gas into the patient and to aninsufflation system and method that can be used in conjunction with aconventional ventilation system without altering the operation of theconventional ventilation system.

[0004] 2. Description of the Related Art

[0005] It is known to reduce rebreathing of exhaled gases in anintubated patient or in a patient with a tracheostomy by providing aflow of insufflation gas, such as oxygen, an oxygen mixture, or othertherapeutic gas, into the distal end of the patient's breathing circuit.FIG. 1 illustrates an example of such a conventional system, commonlyreferred to as a tracheal gas insufflation (TGI) system, in which a flowof insufflation gas is delivered to the airway of the patient. A primaryflow of breathing gas that augments or completely supports the patient'sbreathing is delivered using a conventional ventilator.

[0006] As shown in FIG. 1, an endotracheal tube 30 inserted into anairway 32 of a patient 34 through the oral cavity delivers the primaryflow of breathing gas from a ventilator 36 to the patient's lungs 38. Insuch a conventional ventilation system, a breathing circuit 40 deliversthe primary flow of breathing gas from the ventilator to the patient viaa first limb 42, and exhaled gas from the patient is removed via asecond limb 44. First and second limbs 42 and 44 are typically flexibletubes coupled to endotracheal tube 30 via a coupling member, such as aY-adapter. For purposes of this invention, the breathing circuitincludes all of the structures associated with the ventilation systemthat communicate the primary flow of breathing gas with the airway ofthe patient, such as first limb 42, second limb 44, endotracheal tube 30and any coupling members.

[0007] As the patient inspires, the primary flow of breathing gas isdelivered by ventilator 36 to the patient's respiratory system, i.e.,the airway and lungs, via breathing circuit 40. Typically, the primaryflow of gas delivered to the patient by the ventilator is controlledbased on the total volume delivered, the pressure of the gas delivered,or the patient's respiratory effort, the latter of which is known asproportional assist ventilation (PAV). While an endotracheal tube, whichis passed into the patient's airway via the oral cavity, is illustratedin FIG. 1 as being part of the breathing circuit, it is to be understoodthat other methods for delivering and/or interfacing breathing gas tothe patient, such as a tracheostomy tube, nasal and/or oral mask, or annasal intubated endotracheal tube, are commonly used in conventionalventilation systems as part of the breathing circuit.

[0008] As the patient expires, i.e., breathes out, the exhaled gas,which is laden with CO₂, is removed from the lungs and airway viaendotracheal tube 30 and second limb 44 of breathing circuit 40.Typically, an exhaust valve (not shown) associated with second limb 44and operating under the control of ventilator 36 manages the flow ofexhaust gas from the patient so that, if desired, a certain level ofpositive end-expiratory pressure (PEEP) can be maintained in thepatient's respiratory system. In some ventilation systems, the secondlimb includes an exhaust valve that is controlled by the ventilator butis not contained within the ventilator itself.

[0009] It can be appreciated that at the end of exhalation, not all ofthe exhaled gas containing CO₂, for example, is exhausted to atmosphere.A certain amount of exhaled gas remains in the physiological andanatomical dead space within the patient and in the structural deadspace within the breathing circuit. The structural dead space in thebreathing circuit is the portion of the breathing circuit beginning at adistal end 55 of endotracheal tube 30 or tracheostomy tube to a location46, where the exhalation (second) limb 44 separates from the rest of thebreathing circuit. It is generally desirable to prevent the exhaled, CO₂laden gas in this dead space from being rebreathed by the patient, sothat the patient receives the maximum amount of oxygen or othertherapeutic gas and a minimal amount of CO₂ during each breath. In somepatients, such as patients with cranial injuries, it is imperative thattheir CO₂ level not be elevated.

[0010] Tracheal gas insufflation (TGI) is one method that attempts toremove the exhaled gas from the physiological, anatomical and structuraldead spaces in a patient being treated with a ventilator. Tracheal gasinsufflation involves introducing an insufflation gas, such as oxygen,an oxygen mixture, or other therapeutic gas, into the patient's airway32 at the distal end of breathing circuit 40. In the embodimentillustrated in FIG. 1, an insufflation gas source 48, such as apressurized tank or oxygen or an oxygen wall supply, delivers a flow ofinsufflation gas via a conduit 50 as a stream of gas into the patient'sairway. Conduit 50 is also referred to as an “insufflation catheter.” Ina conventional TGI system, a proximal end of conduit 50 is coupled toinsufflation gas source 48 through a control valve 52, and a distal endof conduit 50 is located generally within or near the distal end ofendotracheal tube 30 so that the flow of insufflation gas is directedtoward lungs 38, as indicated by arrow 54. Typically, the distal end ofconduit 50 is located just above the patient's carina. The oxygen richflow of insufflation gas discharged from the distal end of conduit 50displaces the exhaled air in the anatomical and structural dead spacesso that the patient inhales the fresh (non CO₂ laden) gas on the nextbreath, thereby minimizing rebreathing of CO₂ to keep the patient's CO₂levels as low a possible.

[0011] Conventionally, there are two techniques for delivering the flowof tracheal insufflation gas to a patient. According to a first TGItechnique, the flow of insufflation gas is delivered to the patientcontinuously during the entire breathing cycle while the ventilatordelivers the primary flow of breathing gas to the patient. Thistechnique is commonly referred to as a “continuous TGI system.” Thiscontinuous TGI delivery method, however, has a significant drawback inthat conventional ventilators are not capable of accounting for theadditional volume of gas delivered to the patient by the continuous TGIsystem. As a result, the extra volume of gas bled into the breathingcircuit by the continuous TGI system is simply summed with theprescribed volume of gas being delivered by the ventilator. A possibleoutcome is that an excessive pressure of gas is delivered to thepatient, possibly over-inflating the patient's lungs. This excessivepressure is referred to as “autoPEEP.” A disadvantage associated withautoPEEP is that it increases the patient's work of breathing, becausein order to initiate inspiration, the patient must generate aninhalation force that is strong enough to overcome the autoPEEPpressure. AutoPEEP may also cause tissue damage due to thehyper-inflation of the patient's lungs.

[0012] These problems are dealt with, at least in part, in conventionalcontinuous TGI systems by carefully adjusting the ventilator settings toavoid over-inflation. It can be appreciated that “fooling” theventilator so that the continuous flow of insufflation gas does notover-inflate the patient's respiratory system is not an ideal solutionbecause it does not maximize the operating abilities of the ventilator.The ventilator must be specifically configured to deal with this extrainsufflation gas, rather than being configured as it normally would inthe absence of the flow of insufflation gas. On the other hand,maximizing the operating characteristics of the ventilator by setting itup without accounting for the flow of insufflation gas may result inexcessive CO₂ levels in the patient or hyperinflation of the patient. Inaddition, adjusting the operating characteristics of the ventilator toprevent over-inflation when a continuous TGI system is used requires ahighly trained operator to make the correct fine-tuning adjustments tothe ventilator. Furthermore, this continuous TGI technique requiresconstant monitoring of the patient and ventilator system because changesin the patient's breathing cycle that may require reconfiguring of theventilator or the continuous TGI system can occur in very short timeperiods.

[0013] According to a second TGI technique, referred to as a “phasic TGIsystem,” the flow of insufflation gas is controlled so that theinsufflation flow is only delivered to the patient during the expiratoryphase, preferably at the end, while the exhaust valve associated withthe second limb of the breathing circuit is open. Because the exhaustvalve is open when the flow of insufflation gas is delivered, the extravolume of insufflation gas being delivered to the patient displaces anequal volume of gas out of the breathing circuit through the exhaustport and, therefore, does not over-inflate the patient's lungs. Thisphasic approach, however, requires a relatively complicated controlmechanism for controlling the flow of insufflation gas in conduit 50,for example, by controlling valve 52 using ventilator 36, to ensure thatthe flow of insufflation gas is only delivered while the exhaust valveassociated with second limb 44 is open. It can be appreciated that thisphasic TGI technique increases the complexity and cost of theventilation system and the TGI system due to the precise timing requiredto control the operation of the ventilator and valve 52, so that the gasis delivered at the correct time during the patient's breathing cycle.

[0014] Another drawback associated with conventional TGI systems,including both the continuous and phasic TGI techniques, is thatautoPEEP is also caused by a phenomenon known as stagnation pressure.Stagnation pressure, also known as dynamic pressure, is the pressure orforce generated when a flowing gas is brought to rest by isentropic flowagainst a pressure gradient. The magnitude of the stagnation pressure isproportional to the square of the change in velocity of the gas. Becausethe insufflation gas in a conventional TGI system is directed into thepatient's airway using a relatively small diameter tubing, typically 0.1inch diameter, it has a relatively high velocity, which is deceleratedinto a closed volume, namely the patient's airway and lungs. As aresult, a stagnation pressure is created within the patient, therebyexacerbating the autoPEEP problem. It should be noted that the problemof autoPEEP due to stagnation pressure is prevalent in both thecontinuous and phasic TGI systems because the timing at which the flowof insufflation gas is introduced into the patient does not affect themagnitude of the stagnation pressure generated.

SUMMARY OF THE INVENTION

[0015] Accordingly, it is an object of the present invention to providea tracheal gas insufflation system for introducing a flow ofinsufflation gas into the airway of a patient that overcomes theshortcomings of conventional TGI techniques. This object is achievedaccording to one embodiment of the present invention by providing a TGIsystem that includes an insufflation catheter having a proximal endportion that is located generally outside a patient and a distal endportion that is located in an airway of a patient during use. Theinsufflation catheter provides the flow of insufflation gas to thepatient. A flow control system is coupled between the patient circuit,the insufflation catheter, and a source of insufflation gas to control aflow of gas between the patient circuit, the insufflation catheter, andthe source of insufflation gas. This flow control system allows the userto control the deliver of insufflation gas via the insufflation catheterin an easy and efficient manner.

[0016] In one embodiment of the present invention, the insufflationcatheter includes a vent assembly at the distal end portion of theinsufflation catheter. The vent assembly has first and a second portthat discharges the flow of insufflation gas from the insufflationcatheter. It can be appreciated that a vector force will be associatedwith the discharge of the flow of insufflation gas from each port of thevent assembly.

[0017] In this embodiment, a first port in the vent assembly directs afirst portion of the flow of insufflation gas from the insufflationcatheter generally in a first direction into the patient's respiratorysystem. In addition, a second port directs a second portion of the flowof insufflation gas generally in a second direction out of the patient'srespiratory system. The vent assembly is configured and arranged suchthat a net of all second vector force components associated with theflow of insufflation gas in the second direction is greater than a netof all first vector force components in the first direction responsiveto the flow of insufflation gas exiting the venting means. As in aconventional TGI system, providing the flow of insufflation gas in thefirst direction generates a positive stagnation pressure. However,providing the flow of insufflation gas in the second direction generatesa negative stagnation pressure within the patient. The present inventorsdiscovered that a pressure drop occurs in the patient or in the patientcircuit as a result of the insufflation catheter being placed in thepatient, which tends to increase the positive stagnation pressure.Therefore, the flow of insufflation gas in the second direction shouldbe increased above that in the first direction to counteract thepressure drop in the patient circuit. This ensures that the negativestagnation pressure offsets out the positive stagnation pressure, sothat substantially no stagnation pressure or autoPEEP is generatedwithin the patient.

[0018] The present invention also contemplates directing the flow ofinsufflation gas from the insufflation catheter in a variety ofdirections and locating the distal end of the insufflation catheter in avariety of locations, so long as the net vector force of the expelledgas from the vent assembly is sufficiently low so as to avoid creating aproblematic stagnation pressure in the patient.

[0019] In another embodiment of the present invention, instead of thevent assembly with two ports, two insufflation catheters are provided toaccomplish the same function. The distal end of a first insufflationcatheter directs the flow of insufflation gas in the first directiongenerally toward the patient's lung. The flow in the second direction,generally opposite the first direction to provide a balancing of thepositive and negative pressures created by the flow of insufflation gas,is provided by a second insufflation catheter. Of course, this balancingof pressures may require providing a larger flow of insufflation gas inthe second direction to overcome the pressure drop induced by thepresence of the insufflation catheter or catheters in patient. Thedistal end of the second insufflation catheter is configured andarranged such that, in an operative position, it directs the flow ofinsufflation gas in the second direction, away from the lungs. The flowof gas in the first and second insufflation catheters is providedsubstantially the same so that the combination of flows from thesecatheters performs the same function as the bidirectional vent discussedabove, i.e., the net vector forces resulting from the introduction ofinsufflation gas into the patient's airway at the distal end of thefirst and second insufflation catheter combination is substantiallyzero, thereby minimizing the creation of a stagnation pressure orautoPEEP in the patient.

[0020] It is a further object of the present invention to provide aninsufflation system that does not create significant positive stagnationpressures within the patient and that can be used in a conventionalventilation system to provide a flow of insufflation gas into thepatient's airway. This object is achieved by providing an insufflationsystem as described above and that further includes an exhaust valvedisposed at a portion of the breathing circuit outside the patient. Theexhaust valve is configured and arranged to exhaust gas from thebreathing circuit to ambient atmosphere at an exhaust flow rate thatthat is substantially the same as the flow rate at which theinsufflation gas is introduced into the breathing circuit by the TGIsystem. The flow of insufflation gas into the patient and discharge ofexhaust gas to ambient atmosphere are provided irrespective of theprimary flow of breathing gas to the. The result of this balance betweenthe amount of gas introduced to the breathing circuit and the amount ofgas exhausted from the breathing circuit is that there is no netincrease or decrease in the amount of gas in the breathing circuit.Therefore, no special modification of the ventilator or its operation isneeded.

[0021] This equalization of the flow of gas into and out of thepatient's breathing circuit provided by the TGI system is accomplishedin one embodiment of the present invention by continuously exhaustinggas from the breathing circuit over a range of pressures within thebreathing circuit while the flow of insufflation gas is alsocontinuously introduced into the patient. As a result, gas iscontinuously exhausted from the breathing circuit preferably at the samerate the flow of insufflation gas is introduced into that circuit.

[0022] It is yet another object of the present invention to provide asystem for supplying a therapeutic gas to a patient in which a flow ofinsufflation gas is introduced into the patient's airway without overinflating the patient and without any modification of the operation ofthe gas flow generator, which provides a primary flow of breathing gasto the patient, to account for the excess gas introduced into thebreathing circuit. This object is achieved by providing a system forsupplying therapeutic gas to a patient that includes a first tube thatinserts into a patient's airway for providing a primary flow ofbreathing gas to the patient. An insufflation catheter generallydisposed in the first tube provides a flow of insufflation gas to thepatient at a first flow rate. An exhaust valve is coupled to the firsttube and is configured and arranged to exhaust gas from the first tubeto ambient atmosphere at a second flow rate that is substantially thesame as the first flow rate. The flow of insufflation gas into thepatient and the discharge of exhaust gas to ambient atmosphere areprovided irrespective of the primary flow of breathing gas to thepatient. In one embodiment of the present invention, the exhaust valvecontinuously exhausts gas from the first tube to ambient atmosphere atthe second flow rate despite pressure variations within the first tube.

[0023] It is still another object of the present invention to provide aninsufflation attachment for use with a conventional ventilation system,which provides a primary flow of breathing gas to the patient. Theinsufflation attachment is used to introduce a flow of insufflation gasinto the airway of the patient in a manner that overcomes theshortcomings of conventional insufflation techniques. According to theprinciples of the present invention, this object is achieved byproviding an insufflation attachment that includes a first tube adaptedto be coupled in a breathing circuit. The proximal end of aninsufflation catheter is coupled to the first tube. The insufflationcatheter is configured and arranged such that a distal end portionthereof is generally disposed in an endotracheal or tracheostomy tubewhen the first tube is coupled to the breathing circuit. A vent assemblyis provided at the distal end of the insufflation catheter. The ventassembly has at least one port that discharges the flow of insufflationgas from the insufflation catheter. The vent assembly includes a firstport that directs a first portion of the flow of insufflation gas fromthe insufflation catheter generally in a first direction into thepatient's respiratory system. In addition, a second port directs asecond portion of the flow of insufflation gas generally in a seconddirection out of the patient's respiratory system. The vent assembly isconfigured and arranged such that a net of all vector force componentsin the first direction and in the second direction resulting from thedischarge of insufflation gas into the patient's airway via the ventassembly is substantially zero. As noted above, the positive stagnationpressure created by the flow of insufflation gas in the first directionis offset by the negative stagnation pressure created by the flow ofinsufflation gas in the second direction so that substantially nostagnation pressure is generated within the patient.

[0024] In an alternative embodiment, instead of the vent with two ports,two insufflation catheters are employed. The distal end of a firstinsufflation catheter directs the flow of insufflation gas only in thefirst direction toward the patient's lung, thereby simplifying theconfiguration for this catheter. The opposing flow in the seconddirection opposite the first direction is provided by a secondinsufflation catheter also coupled to the first tube. More specifically,the distal end of the second insufflation catheter is configured andarranged such that, in an operative position, it directs the flow ofinsufflation gas in the second direction, so that the net vector forcesassociated with the flow of insufflation gas from the first and secondinsufflation catheters are substantially zero or so that a greater flowis provided in the second direction to provide additional negativestagnation pressure that offsets the pressure drop induced by thepresence of the insufflation catheter in the breathing circuit.

[0025] It is a further object of the present invention to provide aninsufflation attachment that avoids autoPEEP due to a stagnationpressure and that can be used in a conventional ventilation system inwhich a flow of insufflation gas is continuously introduced into thepatient's airway. This object is achieved by providing an insufflationattachment as described in either of the immediately precedingparagraphs and further comprising an exhaust valve coupled to the firsttube. The exhaust valve is configured and arranged to exhaust gas fromthe first tube, i.e., the breathing circuit, such that the flow rate forthe exhaust gas exiting the breathing circuit is substantially the sameas the flow rate for the insufflation gas introduced into the breathingcircuit by the TGI system. The flow of insufflation gas into the patientand the discharge of exhaust gas to ambient atmosphere are providedirrespective of the primary flow of breathing gas to the patient. Theresult of this balance between the amount of gas introduced to thebreathing circuit and the amount of gas exhausted from the breathingcircuit irrespective of the primary flow of breathing is that there isno net increase or decrease in the amount of gas in the breathingcircuit. Therefore, the ventilator does not “see” the introduction ofthe insufflation gas into the breathing circuit so that no specialmodification of the ventilator or its operation are needed. In oneembodiment of the present invention, exhausting gas from the breathingcircuit is done continuously over a range of pressures within thebreathing circuit at a flow rate that matches the flow rate of theinsufflation gas. As a result, there is substantially no netaccumulation of gas in the breathing circuit due to the introduction ofinsufflation gas into the breathing circuit.

[0026] It is yet another object of the present invention to provide aninsufflation method that overcomes the shortcomings of conventional TGItechniques. This object is achieved by providing a TGI method thatincludes providing a patient circuit adapted to couple a ventilator toan airway of a patient and an insufflation catheter having a proximalend portion located generally outside a patient and a distal end portionadapted to be located in an airway of a patient for providing a flow ofinsufflation gas to such a patient. The method also includes providing asource of insufflation gas and controlling a flow of gas between thepatient circuit, the insufflation catheter, and the source ofinsufflation gas.

[0027] In a further embodiment, the flow of insufflation gas is directedfrom the insufflation catheter such that a net of all vector forcecomponents in a first direction generally into the patient's respiratorysystem and in a second direction generally out of the patient'srespiratory system resulting from discharging the insufflation gas intothe patient's airway is substantially zero. In one embodiment, this isaccomplished by directing a first portion of the flow on insufflationgas in a first direction generally toward the patient's lungs anddirecting a second portion in a second direction generally opposite thefirst direction to minimize or eliminate the generation of stagnationpressure in the patient. As noted above, the present invention alsocontemplates providing a greater flow of gas in the second directionthan is provided in the first direction to overcome the additionalpressure drop imposed by the presence of the insufflation catheter inthe system.

[0028] It is a further object of the present invention to provide aninsufflation method that overcomes the shortcomings of conventionalinsufflation techniques in which a flow of insufflation gas is deliveredto the airway of patient in addition to the primary flow of breathinggas. This object is achieved by providing a method that includes thesteps of (1) delivering the primary flow of breathing gas to the airwayof the patient via a breathing circuit, (2) delivering a flow ofinsufflation gas to the airway of a patient at a first flow rate, and(3) exhausting gas from the breathing circuit to ambient atmosphere at asecond flow rate that is substantially the same as the first flow rate.The flow of insufflation gas into the patient and the discharge ofexhaust gas to ambient atmosphere are provided irrespective of theprimary flow of breathing gas to the patient. In a further embodiment ofthe present invention, the exhaust valve continuously exhausts gas fromthe breathing circuit to ambient atmosphere at the second flow rate overa range of pressures within the breathing circuit.

[0029] It is a still further object of the present invention to providea ventilator and tracheal gas insufflation system. This combined systemincludes a patient ventilation system adapted to generate a flow of gasfor delivery to an airway of a patient and a patient circuit operativelycoupled to the ventilation system for carrying the flow of gas from theventilation system to an airway of a patient. The combined system alsoincludes an insufflation system adapted to generate a flow ofinsufflation gas for delivery to an airway of such a patient, and aninsufflation catheter operatively coupled to the insufflation system forcarrying the flow of gas from the insufflation system to an airway of apatient, wherein a portion of the insufflation system is disposed withinthe patient circuit. A single housing contains both the patientventilation system and the insufflation system.

[0030] These and other objects, features, and characteristics of thepresent invention, as well as the methods of operation and functions ofthe related elements of structure and the combination of parts andeconomies of manufacture, will become more apparent upon considerationof the following description and the appended claims with reference tothe accompanying drawings, all of which form a part of thisspecification, wherein like reference numerals designate correspondingparts in the various figures. It is to be expressly understood, however,that the drawings are for the purpose of illustration and descriptiononly and are not intended as a definition of the limits of theinvention. As used in the specification and in the claims, the singularform of “a”, “an”, and “the” include plural referents unless the contextclearly dictates otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a sectional view illustrating a patient coupled to aventilator and a conventional tracheal gas insufflation system;

[0032]FIG. 2 is a sectional view of a portion of a breathing circuitillustrating the insufflation system of the present invention;

[0033]FIGS. 3A and 3B are side and top views, respectively, illustratingone embodiment of a bidirectional vent for directing the flow ofinsufflation from the insufflation catheter;

[0034]FIG. 4 is a sectional view of a portion of the insulation systemillustrating a further embodiment of the present invention;

[0035]FIGS. 5A-5C are top, side and bottom views, respectively,illustrating another embodiment of a bidirectional vent for directingthe flow of insulation gas in opposite directions from the distal end ofthe insulation catheter, and FIG. 5D is a sectional view taken alongline 5D-5D in FIG. 5B;

[0036]FIGS. 6A-6C are top, side and bottom views, respectively,illustrating yet another embodiment of a bidirectional vent fordirecting the flow of insulation gas in opposite directions from thedistal end of the insulation catheter, and FIG. 6D is a sectional viewtaken along line 6D-6D in FIG. 6B;

[0037]FIG. 7 is a perspective of a further embodiment of a vent assemblythat directs the flow of insufflation gas from the distal end of aninsufflation catheter according to the principles of the presentinvention;

[0038]FIG. 8 is a cross-sectional view of the distal end of theinsufflation catheter shown in FIG. 7;

[0039]FIGS. 9A-9C are perspective, top, and side views illustrating astill further embodiment of a vent for directing the flow ofinsufflation gas from the distal end of the insufflation catheteraccording to the principles of the present invention;

[0040]FIG. 10 illustrates another embodiment of a vent for directing theflow of insufflation gas from the distal end of the insufflationcatheter;

[0041]FIG. 11 is a sectional view of a portion of a breathing circuitillustrating the insufflation system according to yet another embodimentof the present invention;

[0042]FIG. 12 is a sectional view of a distal end portion of a breathingcircuit illustrating a further embodiment of an insufflation system ofthe present invention;

[0043]FIGS. 13 and 14 schematically illustrate other embodiments for aninsufflation system according to the principles of the presentinvention;

[0044]FIG. 15 schematically illustrates another embodiment for anexhaust valve for use in a tracheal gas insufflation system of thepresent invention;

[0045]FIG. 16 is a perspective view of a ventilator and a tracheal gasinsufflation system of the present invention suitable for connection toa patient;

[0046]FIG. 17 is a schematic diagram of a first embodiment of a TGI flowcontrol system according to the principles of the present invention;

[0047]FIGS. 18A-18C illustrate the positions for the valve in the TGIflow control system of FIG. 17 to achieve the desired flow control;

[0048]FIG. 19 is a schematic diagram of a second embodiment of a TGIflow control system according to the principles of the presentinvention;

[0049]FIG. 20 is a flow schematic for the TGI flow control system ofFIG. 19;

[0050]FIG. 21 is a schematic diagram of a third embodiment of a TGI flowcontrol system according to the principles of the present invention;

[0051]FIG. 22 is a schematic diagram of a first embodiment of aventilator/TGI system combination according to the principles of thepresent invention;

[0052]FIG. 23 is a schematic diagram of a second embodiment of aventilator/TGI system combination according to the principles of thepresent invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS OF THEINVENTION

[0053]FIG. 2 illustrates a first embodiment of an insufflation system 56according to the principles of the present invention. For the sake ofsimplicity, FIG. 2 illustrates a portion of the breathing circuit thatcouples the patient with a ventilator, including a distal portion forthe breathing circuit, generally indicated at 58, that inserts into thepatient's airway and a proximal portion, generally indicated at 60, thatremains outside the patient and is coupled to a ventilator (not shown)via a flexible tube or tubes as described above with reference to FIG.1.

[0054] A first tube 62, which is a conventional endotracheal tube ortracheostomy tube, inserts into the patient's airway and attaches to aconventional ventilator breathing circuit for providing a primary flowof breathing gas, generally indicated by arrow 64, to the patient. Aswith conventional TGI systems, insufflation system 56 of the presentinvention includes a second tube 66, which, as noted above, is referredto as an “insufflation catheter,” that provides a flow of insufflationgas to the airway of the patient from a source 68 of such gas.Preferably insufflation catheter 66 is much smaller in diameter thanfirst tube 62 to minimize the resistance to the primary gas flow causedby the insufflation catheter. This additional resistance increases thepressure drop in the first tube that can add to the positive stagnationpressure experienced by the patient.

[0055] In the illustrated embodiment, insufflation catheter 66 is onlycoupled to first tube 66 where the insufflation catheter passes throughthe wall of first tube 62. However, the present invention contemplatesthat the insufflation catheter can be secured to or integral with thewall of first tube 62. For example, a portion of the insufflationcatheter or the entire length of the insufflation catheter can be formedwithin the wall the first tube, which reduces the amount of materialwithin first tube 62 and, hence, flow resistance, thereby maximizing theefficiency of the primary gas flow through the first tube. Source 68,which provides the flow of insufflation gas, such as oxygen, an oxygenmixture, or a therapeutic gas, can be any suitable device, such as apressurized tank of gas, an oxygen concentrator, or a piped wall supplytypically found in hospitals.

[0056] In the embodiment shown in FIG. 2, a proximal end of insufflationcatheter 66 is coupled to source 68 of insufflation gas and a distal endportion is generally located near the distal end portion of first tube62. Typically, the distal end of insufflation catheter 66 is locatedjust above the patient's carina and remains within first tube 62 orextends therebeyond. A vent assembly 70 is provided at the distal end ofinsufflation catheter 66 to control the discharge of insufflation gasinto the patient from the distal end of insufflation catheter 66. Morespecifically, vent assembly 70 is configured and arranged such that acancellation or balancing of vector forces associated with the injectionof the flow of insufflation gas from the distal end of insulationcatheter 66 takes place. That is, the net of all vector force componentsin a first direction generally into the patient's respiratory system(down in FIG. 2) and in a second direction generally out of thepatient's respiratory system (up in FIG. 2) resulting from the dischargeof the flow of insufflation gas into the patient's airway by the ventassembly is substantially zero. As a result, substantially no stagnationpressure is generated in the patient as a result of delivering theinsulation gas into the patient's airway.

[0057] The present inventors discovered that a positive stagnationpressure is generated in the patient relative to the desired PEEP levelwhen the vector sum of all gas discharged generally toward the lungs isgreater than the vector sum of all gas discharged generally away fromthe lung. Similarly, a negative stagnation pressure is generated in thepatient relative to the desired PEEP level when the vector sum of allgas discharged generally away the lungs is greater than the vector sumof all gas discharged generally toward from the lung. The presentinvention further proposed solving the problem of increased positivestagnation pressures that occur with conventional TGI techniques byconfiguring vent assembly 70 so that a balancing of the vector sum ofthese gas streams, and, hence, a balancing of the positive stagnationpressure and the negative stagnation pressure generated by these gasstreams, takes place. That is, the net or total of the vector sum of allgas discharged generally toward the lungs and the vector sum of all gasdischarged generally away from the lung is substantially zero so thatthe generated positive stagnation pressure is offset by a substantiallyequal negative stagnation pressure.

[0058] The present inventors also recognized that the presence of theinsufflation catheter in tube 62 can cause a pressure drop in this tubewhere the catheter is located. As a result, if the flow in the firstdirection 74 is exactly equal to the flow in the second direction 78, apositive stagnation pressure may still be created. That is, the presenceof the insufflation catheter in tube 62, i.e., the flow restrictionimposed by the presence of the insulation catheter in tube 62, preventsthe negative stagnation pressure caused by the flow in the seconddirection from offsetting the positive stagnation pressure caused by theflow in the first direction when the flow in the first and seconddirections are equal. To address this possibility, the present inventioncontemplates making the flow the in the section direction 78 larger thanthe flow in the first direction 74 so that an additional amount ofnegative stagnation pressure is created to account for the pressure dropin tube 62 caused by the presence of the insufflation catheter. As aresult, no significant positive stagnation pressure is generated in thepatient.

[0059] In the embodiment illustrated in FIG. 2, balancing of thenegative stagnation pressure (NEEP) and PEEP is accomplished byproviding a bidirectional vent 70 at the distal end of insulationcatheter 66 that directs the flow of insufflation gas in two oppositedirections. More specifically, a first section 72 directs a firstportion of the flow of insulation gas, indicated by arrow 74, in a firstdirection generally toward the patient's lungs. A second section 76directs a first portion of the flow of insufflation gas, indicated byarrow 78, in a second direction generally opposite the first direction.As with a conventional TGI system, directing a first portion of the flowof insulation gas in first direction 74 creates a positive stagnationpressure within the patient relative to the desired PEEP level. However,this positive stagnation pressure is offset by directing a secondportion of the flow of insufflation gas in second direction 78, whichcreates a negative stagnation pressure NEEP relative to the desired PEEPlevel, so that no net stagnation pressure is created in the patient as aresult of the TGI system of the present invention.

[0060] Preferably, the rate and amount of flow of insufflation gas infirst direction 74 and second direction 78 are equal so that positivestagnation pressure caused by flow in first direction 74 issubstantially cancelled or balanced out by the negative stagnationpressure caused by the flow in second direction 78. It can beappreciated, however, that the flow in first direction 74 and seconddirection 78 need not be exactly equal so long as the differencetherebetween does not result in the generation of an unacceptable levelof stagnation pressure, i.e., autoPEEP. It is also preferable that theexhaust ports in first section 72 and second section 76 are relativelyclose to one another to maximize the cancellation effect of the twoopposite flows. It can be appreciated, however, that proximity betweenthe ports is not a requirement for cancellation within a given tube.Thus, the exhaust ports can be spaced apart from one another over arange of distances so long as the distance between these ports does notreduce the cancellation effect below acceptable levels.

[0061] Furthermore, in the illustrated embodiment, the distal endportion of insufflation catheter 66 is positioned beyond the distal tipof first tube 62 so that both the first flow 74 and second flow 78 ofinsufflation gas originate outside the first tube. This is acceptable solong as the patient's tissues do not impede these flows. The presentinvention also contemplates, however, that one or both of the first andsecond flows 74 and 78 can originate within first tube 62.

[0062] The vent assembly described so far is suited for use with aconventional phasic or continuous flow TGI system. That is, thebidirectional vent can be used with either a phasic or a continuous TGIsystem to reduce or eliminated the stagnation pressure, i.e., autoPEEP,problem. The timing used by the phasic TGI system to ensure that theflow of insufflation gas is provided only at the end of exhalation sothat over-inflation does not occur in combination with the bidirectionalflow of the insufflation gas provided by the bidirectional vent assemblyof the present invention minimizes the autoPEEP resulting from increasedpositive stagnation pressures.

[0063] However, as noted above, the phasic TGI approach remainsrelatively complicated and costly due to the need to control the flow ofthe insufflation gas in synchronization with the patient's breathing.Therefore, it is preferable to provide the insufflation system of thepresent invention in a continuous TGI system. Although a continuous TGIsystem simplifies the delivery of the insufflation gas, conventionalcontinuous TGI systems are inefficient in their use of the ventilator inorder to avoid over-inflation because they require that the operatingsettings of the ventilator be modified from the desired non-TGIsettings.

[0064] A further embodiment of the present invention enablesinsufflation system 56 to be used with a continuous TGI system. This ismade possible by providing an exhaust valve 80 to exhaust a flow of gasfrom the first tube, i.e., breathing circuit 58. In the illustratedembodiment, exhaust valve 80 is provided at a proximal end portion offirst tube 62, which is at the distal end portion of the breathingcircuit, to exhaust a flow of gas from the first tube. It is to beunderstood, however, that the exhaust valve can be provided anywherealong the exhaust limb so long as exhaust valve 80 is located outsidethe patient and vents gases from within the first tube, i.e., thebreathing circuit, to ambient atmosphere, as generally indicated byarrows 82. The present invention contemplates that the functions ofthese exhaust valve described below can be incorporated into the exhaustvalve in the ventilator.

[0065] Exhaust valve 80 configured and arranged to exhaust gas from thefirst tube (breathing circuit) such that the flow rate for exhaust gasexiting the breathing circuit is substantially the same as the flow ratefor insufflation gas introduced into the breathing circuit in thepatient's airway by the TGI system. As a result of this balance betweenthe rate at which insufflation gas introduced to the breathing circuitand the amount of gas exhausted from the breathing circuit, there is nonet increase or decrease in the amount of gas within the breathingcircuit while the TGI system is operating. That is, there is no netchange in the volume of gas in the system over a respiratory cycle as aresult of the presence of the TGI system. Therefore, no specialmodification of the ventilator or its operation are needed. The TGIsystem of the present invention is considered to be “transparent” withrespect to the ventilator.

[0066] In the embodiment illustrated in FIG. 2, exhausting gas fromfirst tube 62 at substantially the same rate the flow of insulation gasenters insufflation catheter 66 is accomplished by continuouslyexhausting gas from the breathing circuit at a relatively constant flowrate over a range of pressures within the first tube while the flow ofinsufflation gas is introduced at substantially the same constant flowrate. As a result, a continuous, non-interrupted, flow of gas isexhausted from the breathing circuit generally at the same rate the flowof insulation gas is introduced into that circuit. In addition, thedischarge of exhaust gas from the breathing circuit to ambientatmosphere are provided irrespective of the primary flow of breathinggas to the patient provided by the ventilator because exhaust valve 80functions independently of the operation of the ventilator.

[0067] Exhaust valve 80 is configured such that the rate of flow of gasto atmosphere through the valve is substantially constant over a rangeof pressures corresponding to the range of pressures provided in thefirst tube during normal operation of the ventilation system. Suchpressure variations in the breathing circuit occur due to changes in theprimary flow of breathing gas provided by the ventilator. As a result ofthe use of this exhaust valve, there is no net accumulation of volume inthe breathing circuit, and, hence, no over-inflation of the patient'slungs even though the insulation gas is continuously provided to thepatient. Furthermore, as noted above, the TGI system is essentially“transparent” to the ventilator, in that no special modification need bemade to the ventilator or its operation in order to provide theinsulation gas to the patient.

[0068] The prevent invention contemplates using exhaust valve 80 incombination with vent assembly 70 in which stagnation pressure isminimized or eliminated as discussed above, so that the dual benefits ofpreventing over-inflation and minimizing stagnation pressure areachieved. However, the present invention also contemplates using exhaustvalve 80 alone, without vent assembly 70. While this latter embodimentmay result in some amount of stagnation pressure being generated in thepatient, such pressure may be acceptable in some situations or held toacceptable levels by, for example, limiting the rate at which theinsufflation gas is provided to the patient. Further, this embodiment,in which only exhaust valve 80 is provided on the first tube, isbeneficial in that the phasic approach to insufflation can be replacedin favor of providing a continuous flow of secondary breathing gas tothe airway of the patient to flush out expired gases. As noted above,providing a continuous flow of insufflation gas is relatively simple andinexpensive and by using exhaust valve 80, the insulation system of thepresent invention avoids over-inflation. Also, the use of exhaust valve80 avoids the need to “fool” the ventilator to account for the extra gasbeing introduced into the patient to prevent over-inflation, so that theoperating capabilities of the ventilator can be maximized and the otherdisadvantages associated with the conventional continuous TGI techniquecan be avoided.

[0069] The present invention contemplates that exhaust valve 80 can haveany configuration that provides a substantially constant rate of exhaustover the desired operating pressures. However, in the exemplaryillustrated embodiment, exhaust valve 80 includes a housing 84 with afirst opening 86 to the interior of first tube 62 and a second opening88 to ambient atmosphere. A diaphragm 90 is provided within housing 84,and an opening 92 is provided in a portion of the diaphragm 90 on a sideof housing 84 generally opposite second opening 88. Exhaust gas flowsfrom opening 92, through a channel 94 between diaphragm 90 and housing84, and out opening 88. Increases in pressure within first tube 62 causediaphragm 90 to deflect upward. This upward movement decreases thecross-sectional area of channel 94 reducing the flow therethrough,thereby providing a constant exhaust flow to atmosphere even though thepressure within the first tube varies.

[0070] An example of a suitable valve that provides these functions isdescribed in U.S. Pat. No. 5,685,296 to Zdrojkowski et al., entitled,“Flow Regulating Valve and Method,” the contents of which areincorporated herein by reference into the present application. However,as noted above, the present invention contemplates that any valve thatprovides these functions can be used in the insufflation system of thepresent invention.

[0071] In the above embodiment, exhaust valve 80 is described ascontinuously venting gas to atmosphere at a rate that substantiallymatches the rate at which insufflation gas is delivered to the patient.It is to be understood, however, that exhausting the gas from thebreathing circuit need not be done continuously, i.e., in anon-interrupted fashion. On the contrary, the present inventioncontemplates that the exhaust vent system of the present inventiondischarges gas from the patient circuit in discrete amounts so long asthe rate at which the gas is exhausted substantially matches the rate atwhich the insufflation gas in delivered to the patient during a timeperiod, such as a breathing cycle.

[0072] The present invention contemplates providing the insufflationsystem of the present invention as an attachment for a conventionalventilation system. According to one embodiment of the presentinvention, the attachment includes insufflation catheter 66, includingthe bidirectional vent at the distal end thereof, and a portion of thefirst tube to which the second tube is attached. Such an attachmentwould simply insert into a conventional breathing circuit by couplingthe portion of the first tube into that circuit with the second tubebeing placed in the patient. Because this embodiment of the attachmentdoes not include exhaust valve 80, it is optimally suited for use with aphasic TGI system. However, by including exhaust valve 80 in theattachment assembly, the insufflation system of the present inventioncan be used with a conventional ventilation system as a continuous TGIsystem without the need to significantly reconfigure the ventilationsystem. The dashed lines in FIG. 2 illustrate exemplary points ofattachment in the breathing circuit for the portion of the first tube towhich the second conduit and exhaust valve are attached. Thus, theattachment can be readily inserted into a conventional ventilationsystem at existing coupling locations for providing insufflation of thepatient's airway.

[0073] A second embodiment of a vent assembly 94 suitable for use at thedistal end portion of insufflation catheter 66 is illustrated in FIGS.3A and 3B. Vent assembly 94 is either attached to or integrally formedwith insufflation catheter 66 and includes a housing 96 that receivesthe flow of insufflation gas from insufflation catheter 66. A first port98 defined in a first end portion 100 of housing 96 directs a firstportion of the secondary flow of breathing gas in the first direction,as illustrated by arrow 74 in FIG. 2. A second port 102 defined in asecond end portion 104 of housing 96 directs a second portion of theflow of insufflation gas in the second direction, as illustrated byarrow 78 in FIG. 2. A channel 106 in housing 96 divides the flow ofinsufflation gas received from insufflation catheter 66 into the firstand second portions and communicates these portions to first and secondports 98 and 102, respectively. The present invention contemplates thatvent assembly 94 is formed separately from the remainder of insufflationcatheter 66 and fixed thereto during manufacture or forming ventassembly 94 as an integral portion of the insufflation catheter.

[0074] A potential concern with vent assemblies 70 and 94 is blockage ofthe exhaust ports. For example, second port 102 may become blocked,either completely or partially, if second end portion 104 slips underthe distal rim of first tube 62 or if the patient's tissues or secretioncollect near the exhaust ports. To minimize this concern, FIG. 4illustrates a positioning assembly 108 for maintaining insufflationcatheter 66 at a generally central location within first tube 62.Positioning assembly 108 includes a collar 110 secured to insufflationcatheter 66 and spokes 112 coupled to collar 108 that keep insufflationcatheter 66 spaced apart from first tube 66. Preferably, at least threespokes are provided to maintain insufflation catheter 66 at a generallycentral axial location within first tube 62, thereby ensuring that flows74 and 78 of gas are not blocked. It is further preferable that spokes112 are made from a flexible material so that the spokes deflect towardinsufflation catheter 66 to maintain the insufflation catheter in thecentral location. It is to be understood that the positioning assemblycan be configured such that the insufflation catheter, or at least thedistal end of the insufflation catheter, is maintained at a locationother than generally along the central axis of the first tube. This canbe accomplished, for example, by making the spoke or spokes on one sideof the collar shorter than the spokes on the other side.

[0075]FIGS. 5A-5D illustrate a third embodiment for a vent assembly 114that attaches to or is integral with the distal end of insufflationcatheter 66. Vent assembly 114 includes a first channel 116 thatreceives the distal end of insufflation catheter 66. In operation, afirst portion 74 of the flow of insufflation gas is expelled from a pairof exhaust ports 118 in a direction generally toward the patient'slungs. A second portion 78 of the flow of insufflation gas is expelledfrom a pair of exhaust ports 120 in a direction generally opposite thefirst direction, i.e., away from the patient's lungs. A second channel122 communicates the flow of insufflation gas from the insufflationcatheter to exhaust ports 118, and a third channel 124 communicates theflow of insufflation gas from the insufflation catheter to exhaust ports120 so that gas is expelled in a direction generally opposite thedirection of the first flow 74. When insufflation catheter 66 isinserted into first channel 116, the exterior surface of insufflationcatheter 66 defines one of the walls of third channel 124 so that secondflow 78 of insufflation breathing gas is expelled from vent assembly 114on either side of the insulation catheter. The embodiment of ventassembly 114 illustrated in FIGS. 5A-5D provides multiple exhaust portson each side of the exhaust vent to minimize the likelihood of blockageof the ports. Thus, the embodiment of FIGS. 5A-5D avoids the need toemploy the positioning assembly of FIG. 4.

[0076]FIGS. 6A-6D illustrate a fourth embodiment for a vent assembly 126that attaches to or is integral with the distal end of insulationcatheter 66. Vent assembly 126 is similar to vent assembly 114 of FIGS.5A-5D except that the exterior surface of the vent assembly 126 is morestreamlined for minimizing flow resistance to the primary flow ofbreathing gas. The generally rounded contours of vent assembly 126 alsominimize friction with the surrounding structures or tissues so that theinsulation catheter can be readily inserted into the patient at theproper position and retracted as well.

[0077] Vent assembly 126 includes a first channel 128 that receives thedistal end of insulation catheter 66. In operation, a first portion 130of the flow of insulation gas is expelled from a pair of exhaust ports132 in a direction generally toward the patient's lungs. A secondportion 134 of the flow of insulation gas is expelled from a pair ofexhaust ports 136 in a direction generally opposite the first direction,i.e., away from the patient's lungs. A second channel 138 communicatesthe flow of insulation gas from the insufflation catheter to exhaustports 132, and a third channel 140 communicates the flow of insufflationgas from the insulation catheter to exhaust ports 136 so that gas isexpelled in a direction generally opposite the direction of the firstflow 130. When insufflation catheter 66 is inserted into first channel128, the exterior surface of insufflation catheter 66 defines one of thewalls of third channel 140 so that second flow 134 of insufflation gasis expelled from vent assembly 126 on either side of the insulationcatheter.

[0078]FIGS. 7 and 8 illustrate a fifth embodiment of a vent assembly142. In this embodiment, vent assembly 142 is defined by providing aplurality of exhaust ports 144 directly in the distal end of insulationcatheter 66. As in the previous embodiments, a first set of ports 146direct a first portion of the flow of insulation gas 148 in a firstdirection generally toward the patient's lungs, and a second set ofports 150 direct a second portion of the flow of insufflation gas 152 ina second direction generally away from the patient's lungs. The presentinvention contemplates that each set of ports can include one or moreexhaust ports.

[0079] The first and second sets of exhaust ports are defined ininsufflation catheter 66 such that the vector forces associated withfirst and second portions 148 and 152 of the flow of insulation gastherefrom are offsetting along the proximal/distal axis, i.e., thelengthwise axis of the catheter. For example, as shown in FIG. 8, firstand second sets of ports 146 and 150 are configured and arrangedrelative to one another such that the net of the vector forcesassociated with the flow of gas along the x-axis is substantially zero.In addition, the exhaust ports in the second set of ports are configuredand arranged such that the net of the vector forces associated with theflow of gas along the y-axis is also substantially zero. It should benoted that in this embodiment, there is no y-component associated withthe vector force produced by first portion 148 of breathing gas exitingfrom exhaust port 146. As a result of this configuration, the net or thevector forces associated with the discharge of insufflation gas from theinsulation catheter in the first direction generally toward the lungsand in the second direction generally away from the lungs issubstantially zero, so that substantially no stagnation pressure isgenerated as a result of injecting the insufflation gas into thepatient's airway. Although not shown in FIGS. 7 and 8, it should befurther noted that the exhaust ports in the second set of ports arepreferably configured and arranged around the circumference ofinsufflation catheter 66 such that the net of the vector forcecomponents associated with the flow of gas in the yz-plane is alsosubstantially zero.

[0080] As noted above, the present invention also contemplates formingthe first and second sets of ports such that the net of all the secondvector force components in the second direction, i.e., in the negative xdirection in FIG. 8, is greater than the net of all the first vectorforce components in the first direction, i.e., in the positive xdirection. As a result, the pressure drop created by the presence of theinsufflation catheter in the patient circuit is offset, and there is nosignificant positive stagnation pressure created in the patient as aresult of the flow of insufflation gas exiting the insufflation cathetervia the first and second ports.

[0081]FIGS. 9A-9C illustrate a sixth embodiment of a vent assembly 154that attaches to or is integral with the distal end of insufflationcatheter 66. In this embodiment, vent assembly 154 includes a pluralityof exhaust ports 156 that lie in generally the same plane, whichcorresponds to the yz-plane located along a lateral axis 158 of the ventassembly. Balancing of the forces in the axial direction of insufflationcatheter 66, i.e., along the x-axis shown in FIGS. 9A and 9C, isaccomplished in this embodiment because there are no vector componentsfor the flow of insufflation gas in the x-direction (positive ornegative). That is, by directing the insufflation gas in a substantiallylateral direction within a patient, which is generally perpendicular tothe first and the second directions (along the x-axis), so that the flowof insufflation gas is directed neither into nor out of the patient'srespiratory system, the net of all vector force components in a firstand second directions resulting from the discharge of the flow ofinsufflation gas into the patient's airway by the vent assembly issubstantially zero. Thus, no stagnation pressure is generated. It isbelieved, however, that because there are no vector components for theflow of insufflation gas in the positive x-direction, i.e., directedinto the patient's respiratory system, this embodiment of the presentinvention may not provide optimize the gas purging function as well asthe other embodiments because it does not direct a stream of gasgenerally into the lungs.

[0082] In the embodiment illustrated in FIGS. 9A-DC, the net of thevector forces associated with the flow of insufflation gas from ports156 in the yz-plane, which is a plane in which lateral axis 158 lies, isalso zero. This is accomplished by providing a symmetrical distributionof the flows from vent assembly 154 about a central axis 160. Thus, bydirecting the flow of insufflation gas in a lateral direction, thisembodiment of the vent assembly for use in the TGI system of the presentinvention ensures that the net vector forces associated with thedischarge of insufflation gas from the insufflation catheter in thefirst and second directions (into and out of the patient) aresubstantially zero, so that substantially no positive or negativestagnation pressure is generated as a result of injecting the flow ofinsufflation gas into the patient's airway. In addition, the dischargeof insufflation gas in the yz-plane is arranged such that the net of thevector forces in the y-plane is also zero. Thus, the total net forces inall directions is also zero for this embodiment.

[0083] In this embodiment, the vector forces in the yz-plane areoffsetting (balanced) due to the symmetrical distribution of flow fromthe vent assembly about axis 160. It is to be understood, however, thatthe net vector forces in the yz-plane, i.e., in a lateral direction,which is generally perpendicular to the longitudinal axis of theinsufflation catheter, need not be offsetting. If this is the case, thedistal end of the catheter will be urged in a certain direction oppositethe side of the catheter releasing the greater net vector flow. If thedistal end of the insufflation catheter is within the endotracheal ortracheal tube, it will be urged against the inside wall of the tube.Likewise, if the distal end of the insufflation catheter is outside theendotracheal or tracheal tube, it will be urged against the patient'stissues. Either of these outcomes may be acceptable so long as theinsufflation catheter accomplishes its function of discharginginsufflation gas into the patient's airway while minimizing thegeneration of stagnation pressures. It is to be further understood thatthe number of ports defined in the vent assembly can be varied. However,it is preferable that the number and location or pattern of the ports beprovided such that the net vector forces in the y-direction arebalanced.

[0084] In the embodiment illustrated in FIGS. 9A-9C, vent assembly 154is an element that is provided on the distal end of the insufflationcatheter. It is to be understood, however, that the vent assemblyillustrated in FIGS. 9A-9C, where the flow of insufflation gas isprovided in only the lateral direction, can be accomplished by definingexhaust ports 156 directly in the distal end of insufflation catheter66, as done in the embodiment illustrated in FIGS. 7 and 8. Such anarrangement has many advantages, including, for example, decreasing thesize of the distal end of the insufflation catheter, minimizing thenumber of parts for the TGI catheter, and reducing manufacturing costs.In addition, the lateral discharge of insufflation gas within thepatient can be accomplished by locating the distal end of theinsufflation catheter within the patient such that the stream ofinsufflation gas is directed neither into nor out of the patient'srespiratory system.

[0085] It can be appreciated from the six embodiments described above,that there are a variety of ways in which the secondary gas can bedirected from the distal end of the insufflation catheter whileminimizing, and preferably eliminating, the creation of stagnationpressure. FIG. 10 illustrates yet a seventh example of a vent assembly162 for accomplishing this purpose. Vent assembly 162 attaches to or isintegral with the distal end of insufflation catheter 66.

[0086] In FIG. 10, vent assembly 162 includes a plurality of ports164-170 that direct the flow of insufflation gas from the vent assemblyas indicated by arrows 172-178, which are at a non-zero angle relativeto longitudinal axis 175 of the insufflation catheter. Ports 164-170 aredisposed on vent assembly 162 such that the vector forces resulting fromthe injection of insufflation gas from the vent assembly that areparallel to the x-axis (longitudinal axis 175) are offsetting, i.e., sothat there is substantially no net vector force along the x-axis. Asnoted above, this configuration reduces or eliminates the creation of astagnation pressure in the patient. It is preferable that the vectorforce components resulting from the injection of insufflation gas fromthe vent assembly that are parallel to the y-axis (lateral axis 177) arealso offsetting, i.e., so that there is substantially no net vectorforce along the y-axis or the z-axis. It is to be understood, however,that a balancing of forces in the yz-plane is not necessary for thepurpose of eliminating stagnation pressure. Although four ports areillustrated in FIG. 10, it is to be understood that as few as two ormore than four ports can be provided so long as the balancing function,where the net vector force into and away from the patient's lungs aresubstantially zero, is achieved.

[0087] In all of the seven above-described embodiments, the ports directthe flow of insufflation gas from the vent assembly such that the vectorforces of the flow of insufflation gas, at least with respect to thex-axis, are offsetting. That is the net flow down in FIG. 10 (generallytoward the patient's lungs) is offset by an equal net flow up (generallyaway from the patient's lungs). The result of this balancing of the netvector forces in the x-direction is a minimization or elimination ofstagnation pressures in the patient that would otherwise result from theinjection of the flow of insufflation gas into the patient's respiratorysystem. Please note that the x and y coordinates in FIG. 10 areintentionally oriented in the manner illustrated, i.e., rotated fromwhat is generally considered conventional, to correspond with theorientation for these coordinates shown in FIGS. 8 and 9C, where thex-axis is parallel to the longitudinal axis of the insufflationcatheter.

[0088] One can appreciate that reducing or preventing the generation ofa stagnation pressure does not require that the flows from the ventassembly be directly opposite one another, such as up and down shown inFIGS. 2-6C. Quite the contrary, as shown in FIGS. 7, 8, and 10, theflows from the vent assembly can be provided in a variety of directionsso long as the net vector force components generally toward thepatient's lungs (into the patient) are offset by a substantially equalnet vector force component generally away from the patient's lungs (outof the patient).

[0089] A still further embodiment of the present invention isillustrated in FIG. 11. In the previous embodiments, the TGI systemincludes a single insufflation catheter with a vent assembly at itsdistal end, where the vent assembly includes one or more ports fordirecting the flow of insufflation gas in an offsetting or zero netforce fashion. In the embodiment shown in FIG. 11, however, a pair ofinsufflation catheters 180 and 182 are provided in first tube 62 inplace of the single insufflation catheter 66 of the previousembodiments. More specifically, first insufflation catheter 180 is agenerally straight tube that directs a portion of the flow of insulationgas in a first direction indicated by arrow 184 generally toward thepatient's lungs or into the patient. Second insulation catheter 182, onthe other hand, has a distal end portion that directs another portion ofthe flow of insufflation gas in a second direction indicated by arrow186, which is generally opposite the first direction, i.e., generallyaway from the patient's lungs or out of the patient. The flow ininsufflation gas in direction 186 produces a negative stagnationpressure that offsets or cancels out the positive stagnation pressurecreated by the flow of insufflation gas out of first insufflationcatheter 180. As noted above, it is not necessary that flows 184 and 186be directed exactly as shown so long as the vector forces in the firstand second directions into and out of the patient along the patient'sairway associated with the two flows are offsetting, so thatsubstantially no stagnation pressure is generated in the patient. Ofcourse, the insufflation catheters can be configured to provide morethan one flow and more than two catheters can be provided, so long asthe net vector force of all of the flows of the secondary gas from allof the insufflation catheters in the lengthwise axial direction issubstantially zero.

[0090] In a preferred embodiment of the present invention, the proximalends of insulation catheters 180 and 182 are commonly connected to thesource of secondary breathing gas so that the flows 184 and 186 out ofinsulation catheters 180 and 182, respectively, are substantially equaland, hence, offsetting. It is to be understood, however, that eachinsulation catheter can be supplied with gas from an independent gassource.

[0091] As with the embodiment illustrated in FIG. 2, the insulationsystem of FIG. 1I can be configured as an attachment for a conventionalventilation system. For a phasic TGI system, exhaust valve 80 need notbe provided in the attachment. The dashed lines in FIG. 11, like thosein FIG. 2, illustrate exemplary coupling locations for the portion offirst tube 62 in the breathing circuit, with insufflation catheters 180and 182 being directed into the endotracheal or tracheostomy tube forremoving exhaled gases, once the portion of the first tube between thedashed lines is coupled in the breathing circuit.

[0092] The embodiment illustrated in FIG. 11 is advantageous in that itsimplifies the structure for simultaneously providing a flow ofinsufflation gas in opposing directions within the patient's airway.However, this embodiment requires providing multiple insufflationcatheters within first tube 62, which may increase the resistance toflow through the first tube. This can be minimized, however, byproviding at least a portion of insufflation catheter 180 and/orinsufflation catheter 182 integral with or within the wall of first tube62. The present invention also contemplates providing the entire lengthof one or both on the insufflation catheters within the wall of firsttube 62. FIG. 12 illustrates an embodiment of the present invention inwhich the insufflation catheter is formed as a conduit provided in thewall of first tube, which is typically an endotracheal or nasotrachealtube. For the sake of illustration, FIG. 12 illustrates a variety oftechniques by which the insufflation gas can be delivered to the patientusing an insufflation catheter formed within the wall of the distalportion of the breathing circuit, e.g., the endotracheal or nasotrachealtube. The present invention contemplates using any one of thesetechniques or any combination of these techniques to deliver theinsufflation gas to the airway of the patient. This embodiment of thepresent invention is advantageous in that it eliminates the resistanceto flow within the endotracheal or nasotracheal tube imposed by theinsufflation catheter. This flow restriction causes by the present ofthe insufflation catheter in the breathing circuit is also believed tobe a factor that contributes to the increased autoPEEP in conventionalTGI system because the patient must exhaled against a more restrictedflow than would otherwise be the case without the presence of the TGIsystem.

[0093] As shown in FIG. 12, insufflation system 189 includes a firsttube 191 that inserts into a patient's airway for providing a primaryflow of breathing gas to the patient. A conduit 193 is defined withinthe wall of first tube and a port 195 is provided for coupling conduit193 to an insufflation gas source (not shown). Conduit 193 carries theinsufflation gas to the distal end portion of first tube 191 in the samemanner as insufflation catheter 66. In the previous embodiments, thevent assembly is configured so as to discharge gas from the insufflationcatheter generally in a first direction toward the patient and in asecond direction generally out of a patient so that the net vectorcomponents in the lengthwise direction are substantially zero, therebyminimizing the generation of stagnation pressure in the patient. Thissame function is achieved in this embodiment by controlling thedirection of flow for the insufflation gas exiting conduit 193. FIG. 12illustrates several techniques for discharging insufflation gas from thedistal end of first tube 190.

[0094] According to a first technique, a pair of ports 195 and 197 areprovided to communicate the insufflation gas from a conduit 193 to theairway of the patient. Port 195 directs a first portion of the flow ofinsufflation gas in the first direction, as indicated by arrow 199,generally toward the patient's lungs, and port 197 directs a secondportion of the flow of insufflation gas in the second direction, asindicated by arrow 201, generally away from the patient's lungs. As inthe previous embodiments, the vector components associated with firstand second flows 199 and 201 of insufflation gas are preferablyoffsetting, at least along the lengthwise axis of catheter 190, so thatno stagnation pressure is generated in the patient. According to asecond technique, this same result is achieved by providing two or moreseparate ports 203 and 205 in the wall of tube 190, with each portdirecting a portion of the flow of insufflation gas either generallytoward or generally away from the lungs of the patient.

[0095] Instead of providing a pair of ports 207 in the inside wall offirst tube 190, a third technique of delivering the insufflation gasfrom tube 190 includes providing a port 209 in a distal surface 211 ofthe first tube to direct a portion 213 of the flow of insufflation gasin the first direction generally toward the patient's lungs. Thisembodiment is believed to be advantageous in that is directs a portionof the insufflation gas directly into or down the patient's airway. Asecond port, such as port 205, is provided to deliver another portion ofthe insufflation gas in a second direction generally out of the patientso that flow 213 is offset by the flow out of port 205 so that a pair ofports 215 accomplish the same function of no net stagnation pressure asthe vent assembly of the previous embodiments.

[0096] The present invention contemplates that other ports, such as port217, can be provided on the inside wall of tube 190 to direct a portionof the insufflation gas laterally, as discussed above with respect toFIGS. 9A-9C. In addition, the present invention contemplates providingone or more ports for directing the insufflation gas as described aboveone the outside wall of tube 190. However, it is believed that such aconfiguration would not be advantageous due to the small clearance thatis believed to exist between the outside wall of tube 190 and in surfaceof the patient's airway.

[0097]FIG. 12 illustrates a variety of techniques for discharging theinsufflation gas from a conduit defined in the wall first tube 190. Thepresent invention contemplates using any one of these techniques, or anycombination of these techniques, to deliver the insufflation gas to theairway of the patient. For example, multiple ports similar to port 209can be provided in the distal end of tube and multiple ports similar toport 205 can be provided to deliver the offsetting flow of insufflationgas.

[0098] As discussed above, the present invention contemplates using theinsufflation with a continuous flow TGI system by providing exhaustvalve 80 in a portion of first tube 62. Exhaust valve 80 continuouslyexhausts gas from the first tube at substantially the same rate as theflow of insufflation gas is introduced into the breathing circuit toproduce a balance between the amount of gas introduced to the breathingcircuit and the amount of gas exhausted from the breathing circuit. As aresult, there is no net increase or decrease in the amount of gas in thebreathing circuit. This requires regulating the flow rate of theinsufflation gas into the TGI system and/or regulating the flow ofexhaust gas from the system so that the two flow rates are substantiallyequal.

[0099] In the above described embodiment, exhaust valve 80 exhausts gasfrom the system at a rate that cannot be changed unless the exhaustvalve is replaced with another exhaust valve having a different exhaustflow rate. That is, exhaust valve 80, due to its fixed configuration,exhausts gas at a given rate. For this reason, in operation, thecaregiver or user of the TGI system must regulate the rate of flow ofthe insufflation gas into the patient to match the given rate of exhaustfrom exhaust valve 80. It is preferable, however, to allow the caregivergreater flexibility in selecting the rate at which the flow ofinsulation gas is introduced to the patient without having to take intoconsideration the exhaust rate of the exhaust valve. Techniques foraccomplishing this function are discussed below with reference to FIGS.13-15.

[0100] In the embodiment shown in FIG. 13, a flow control assembly 190is provided that ensures that the rate at which gas is exhausted fromthe breathing circuit, as indicated by arrow 192, substantially matchesthe rate at which the insufflation gas is introduced into the patient'sairway, as indicated by arrow 194. An example of a suitable flow controlassembly for accomplishing this function is a paddlewheel valve, whereinthe incoming gas flow 194 turns one side of a paddlewheel 196. The otherside of paddlewheel 196 is provided in the exhaust path from thebreathing circuit 58. The paddlewheel in configured such that turningone side of the wheel via flow 194 draws out or allows an equal amountof flow 192 to exit the breathing circuit. As a result, there is no netaccumulation of gas in the breathing circuit. Because the rate of flow194 into the breathing circuit via the TGI system controls the speed atwhich the paddlewheel turns, and, hence, the rate at which flow 192exhausts from the breathing circuit, the caregiver can freely select anyrate of flow for the introduction of the insulation gas into the patientand flow control assembly 190 will automatically ensure that asubstantially equal exhaust flow is provided from the breathing circuit.

[0101] While FIG. 12 illustrates a paddlewheel configuration for flowcontrol assembly 190 to ensure that the flow out of the breathingcircuit is substantially the same as the flow into the breathing circuitprovided by the insulation catheter, it is to be understood that thepresent invention contemplates other configurations for flow controlassembly 190 that accomplish this function. For example, a flow orvolume meter can be provided that measures the rate or volume of gasintroduced into the breathing circuit via the TGI system, and a flowcontrol valve can be provided in the exhaust path, with the flow controlvalve controlling the rate of exhaust to atmosphere based on the outputfrom the flow or volume meter.

[0102] Another technique for ensuring that the flow out of the breathingcircuit matches the flow of insufflation gas into the circuit providedby the TGI system while allowing the caregiver to select the rate forthe flow of insufflation gas provided by the TGI system is shown in FIG.14. In this embodiment, a first flow of gas 200 from source 68 isseparated by a bypass valve 202 into a secondary flow 204 that isprovided to the TGI system and a bypass flow 206. Bypass flow 206 isintroduced into breathing circuit 58 at any location that allows thisbypass flow to exhaust from the breathing circuit via exhaust valve 80,as discussed above.

[0103] The rate of first flow 200 and the rate of exhaust 208 fromexhaust valve 80 should match one another as in the embodiment of FIG.2. However, this embodiment allows the caregiver to select the rate atwhich the insufflation gas is provided by insufflation catheter 66 byselecting the flow rate for secondary flow 204, with the remainder ofthe first flow of gas 200 being diverted by bypass valve 202 andintroduced in the breathing circuit without being delivered to theinsufflation catheter. Total flow 200 into the breathing circuit, i.e.,secondary flow 204+bypass flow 206, should match the total flow 208continuously exhausted from the breathing circuit. The amount of gasprovided to the breathing circuit via bypass flow 206 will change as theuser or caregiver changes the amount of gas provided via the TGI system.However, the total flow into the breathing circuit will always match thetotal flow out of the breathing circuit regardless of the flow rate ofthe flow of insufflation gas provided via the TGI system. Thus, oneexhaust valve 80 having an exhaust flow rate that matches the rate offirst flow 200 can be used in the TGI system, while allowing thecaregiver to vary the rate at with the insufflation gas (second flow204) is delivered to the patient's airway by changing the amount of gasdiverted in bypass valve 202.

[0104] It should be noted that the TGI system shown in FIG. 13, and, inparticular, bypass valve 202 and/or the system for providing bypass flow206 should be designed to account for the fact that the TGI systemimposes a relatively significant flow restriction on the flow of gas tothe patient's airway via insufflation catheter 66. For example, thepresent invention contemplates providing a flow restriction with respectto bypass flow 206, where the flow restriction imposed on bypass flow206 substantially matches the flow restriction presented by the TGIsystem so that the proper amount of insufflation gas is provided to theinsufflation catheter.

[0105]FIG. 15 illustrates yet another technique for ensuring that theflow out of the breathing circuit matches the flow of insufflation gasinto the circuit provided by the TGI system so that the caregiver hasflexibility in selecting the rate for the flow of insufflation gas intothe patient's airway. In this embodiment, exhaust valve 210 isconfigured such that the flow rate through the exhaust valve varies withthe flow rate of insufflation gas delivered to the patient via the TGIsystem. Exhaust valve 210 is substantially similar to exhaust valve 80in that it is a constant flow valve that allows a constant rate ofexhaust from the breathing circuit to atmosphere despite fluctuations inthe pressure of gas in breathing circuit 58. The main difference betweenexhaust valve 210 and exhaust valve 80 is that the dimensions of theexhaust pathway through the valve, such as width d of channel 228, varyin valve 210 based on the flow of the secondary gas into the patient,thereby controlling the rate at which gas vents to atmosphere throughvalve 210. In this respect, it can be appreciated that exhaust valve 210provides the same general function provided by flow control assembly 190in FIG. 13. In exhaust valve 80, the dimensions of channel 94 do notvary based on the flow of insufflation gas to the patient.

[0106] As shown in FIG. 15, exhaust valve 210 includes a housing 212defined by a first member 214 and a second member 216, which aremoveably coupled to one another via a flexible membrane 218 so that thefirst and second members 214 and 216 can move toward and away from oneanother. A first opening 220 is provided in second member 216 thatcommunicates the interior of housing 212 with first tube 62 in breathingcircuit 58, and a second opening 222 is provided in first member 214. Adiaphragm 224 is provided within housing 212, and an opening 226 isprovided in a portion of diaphragm 218 on a side of housing 212generally opposite second opening 216. Exhaust gas flows from openings220 and 226, through a channel 228 between diaphragm 224 and firstmember 214, and out opening 222, as indicated by arrows A and B. Exhaustvalve 210 also includes a support structure 230 fixed to second member216 for supporting a piston and cylinder arrangement that is used tomove first member 214 relative to second member 216. An opening 231 isdefined in support structure 230 to communicate channel 228 toatmosphere, as indicated by arrow B. A piston 232 is provided incylinder 234 so as to define a chamber 236 that is closed relative tothe ambient atmosphere. One end of piston 232 is coupled to first member214 so that movement of the piston also moves first member 214 relativeto second member 216, thereby altering the dimensions of channel 228,such as width d of channel 228, to alter the flow rate of gas from tube62 to atmosphere.

[0107] As in the previous embodiments, a source 68 of the secondary gasis provided to the breathing circuit via insufflation catheter 66 in theTGI system. In this embodiment, however, the secondary gas alsocommunicates with chamber 236 so that a pressure differential existsbetween chamber 236 on the interior side of piston 232 and ambientatmosphere on the exterior side of piston 232. Communicating the flow ofinsufflation gas to chamber 236 causes piston 232 to move, as indicatedby arrow C, based on the flow rate, and, likewise, the pressure level,of the flow of insulation gas into the breathing circuit. Movement ofpiston 232, in turn, moves first member 214 relative to second member216, which changes the width d of channel 228, thereby changing the rateat which gas exhausts from the breathing circuit in proportion to therate at which the flow of insufflation gas is provided to the breathingcircuit via the TGI system. For example, as the rate of the flow ofinsulation gas increases, the pressure in chamber 236 increases, movingpiston 232 upward to increase the dimensions of channel 228 so that moregas exhausts from tube 62. Preferably, exhaust valve 210 is configuredsuch that the increase or decrease in the rate of exhaust gas issubstantially the same as the corresponding increase or decrease in therate of flow of insulation gas provided by the TGI system.

[0108]FIG. 16 illustrates a ventilator 300 and a tracheal gas insulationsystem, generally indicated at 302, according to the principles of thepresent invention about to be connected to a patient 304. A patientcircuit 306 communicates ventilator 300 with an airway of a patient. Inthe illustrated embodiment, an endotracheal tube 308 is shown connectingthe ventilator to the patient. It is to be understood that the presentinvention contemplates connecting the patient and the ventilator in anyconventional manner, such as via a tracheotomy tube. Patient circuit 306includes an inspiratory limb 310 and a expiratory limb 312.

[0109] TGI system 302 includes a source of TGI gas. In the illustratedembodiment, an oxygen tube 314 is connected to an source of oxygen (315in FIG. 17) and an air inlet tube 316 is connected to a source of air(317 in FIG. 17). Oxygen tube 314 and air inlet tube 316 are connectedto a blender 318 that is used to set the fraction of inspirited oxygen(FIO₂) to be provided by the TGI system. An outlet 319 of blender 318 isprovided to a TGI flow control system 320 that is coupled betweenpatient circuit 306, insufflation catheter 322, and the source ofinsufflation gas. Flow control system 320 controls a flow of gas betweenthe patient circuit, the insulation catheter, and the source ofinsufflation gas.

[0110] TGI system 302 includes a first outlet line 324 that connects theTGI flow control system 320 to patient circuit 306. More specifically,outlet line 324 connects TGI flow control system 320 to expiratory limb312. An exhaust valve 326 is provided in expiratory limb 312. In oneembodiment of the present invention, exhaust valve 326 corresponds toexhaust valve 80, as discussed above, and provides a constant rate ofexhaust regardless of the pressure in the expiratory limb. This enablesthe overall ventilation/TGI system to remove substantially the samevolume of gas that is introduced into that system via the insufflationcatheter in the TGI system over a given period of time, such as onerespiratory cycle.

[0111] A second outlet line 330 from TGI flow control system 320 isprovided to a heated humidifier 332, which heats and humidifies the gasflowing from TGI flow control system 320 into insufflation catheter 322.A control line 334 is provided from TGI flow control system 320 toheated humidifier 332 to control the operation of the heater in theheated humidifier. A processor (not shown) in TGI flow control system320 controls the operation of heated humidifier 332 via a signal orpower provided on control line 334. It is to be understood thathumidifier 332 can have any conventional configuration, can be anon-heated humidifier, and can be eliminated if heat or humidificationis not desired.

[0112] In the illustrated embodiment, a distal end portion ofinsufflation catheter 322 selectively inserts into endotracheal tube 308to deliver the insufflation into the patient's airway. The presentinvention also contemplates providing a suction catheter 336 connectedto a vacuum source (not shown) that is controlled by a suction controlvalve 338. Insufflation catheter 322 and suction catheter 336 can bealternatively placed in the patient's airway using any conventionaltechnique. Various embodiments for TGI flow control system 320 arediscussed below with respect to FIGS. 17-21.

[0113] TGI flow control system 320 controls the rate the insufflationgas is delivered to TGI system 302 and regulates the pressure of theinsufflation gas. This is accomplished by means of pressure regulators340 and 342 coupled to output line 319 from blender 318, which is thesource of insufflation gas to the TGI system. It is to be understoodthat the two regulators shown in FIG. 17 can be replaced with a singleregulator. In addition, further regulators can be added to step down thepressure as needed. In a preferred embodiment, the final pressure forthe insufflation gas at the output of the last regulator isapproximately 25 psi. Of course, the regulators can be eliminated if thepressure of the gas entering the TGI flow control system is already atthe desired pressure.

[0114] Control system 320 also includes valving to control the flow ofinsufflation gas between (1) the source of insufflation gas, whichcorrespond to output 319 of blender 318, (2) patient circuit 312 viaoutlet line 324, and (3) insufflation catheter 322. To this end, controlsystem 320 includes a main shutoff valve 344 that is coupled to outlet346 of regulator 342. An optional pressure sensor 348 is provided at aninlet to the main shut valve.

[0115] A needle valve 350 disposed in line 345 controls the rate atwhich the insufflation gas flows into the TGI system. It is to beunderstood that the present invention contemplates using anyconventional technique for controlling the flow of gas to the TGIsystem. For example, an orifice plate can be used in place of the needlevalve. Another optional pressure sensor 352 monitors the ambientatmospheric pressure. The atmospheric pressure is used to compensate theother measured parameters for changes in atmospheric pressure.

[0116] A bypass valve 354 and a vent valve 356 are provided in seriesbetween the source of insulation gas (the output of flow regulatingvalve 350), patient circuit via outlet line 324, and insulation catheter322 via outlet line 330. Valves 354 and 356 are three-way valves thatcan be moved between two positions. The control of these valve is shownin FIGS. 18A-18C. Note that FIGS. 18A-18C do not show flow regulatingvalve 350.

[0117] In a TGI configuration shown in FIG. 18A, valves 354 and 356communicate the insufflation catheter with the source of insufflationgas and disconnect the patient circuit from the source of insufflationgas and from the insulation catheter. This enables a flow ofinsufflation gas from the insufflation gas source to the insufflationcatheter for delivery to the airway of the patient. More specifically,valve 354 is in an “enabled” position to communicate gas from line 345to line 358 and disconnects all other flow paths. Valve 356 is alsoenabled to communicate gas from line 358 to line 330, and disconnectsall other flow paths.

[0118] A “bypass” configuration for valves 354 and 356 is shown in FIG.18B. This bypass configuration is needed when the user does not want aflow of insulation gas to be delivered to the insufflation catheter, butalso does not want to disconnect the TGI system. This occurs, forexample, where the caregiver desired to suction the patient to removesecretions. In this situation, there still is a continuous exhausting ofgas from the TGI system as discussed above do the presence of exhaustvalve 80 or 326. Therefore, there is still a need to input an equalamount of gas into the TGI system, but not into the insulation catheter.This is accomplished by providing the flow of insufflation gas, butbypassing it from the insufflation catheter. Instead, the flow ofinsufflation gas is delivered directly to patient circuit 306, where theconstant flow exhaust assembly 326 is provided. In the bypassconfiguration, valve 354 is disabled, thereby communicating gas fromline 345 to line 324 and disconnects all other flow paths. Valve 356 isenabled as noted above so that gas flows from the source of insufflationgas to the patient circuit and not to the TGI catheter.

[0119] Finally, a “vent” configuration for valves 354 and 356 is shownin FIG. 18C. This vent configuration allows the insufflation catheter toprovide a path from the patient's lungs to the ambient atmosphere viathe patient circuit. The source of insufflation gas is also preventedfrom being delivered to the insufflation catheter. In the ventconfiguration, valve 354 is disabled and valve 356 is also disabled tocommunicate line 330 with line 324 and disconnect all other flow paths.

[0120] The following table summarizes the position for bypass valve 354and vent valve 354. Of course, the main shutoff valve 344 is enabled inthese modes of gas delivery. Bypass Valve 354 Vent Valve 356 TGI ModeEnabled Enabled Bypass Mode Disabled Enabled Vent Mode Disabled Disabled

[0121] A pressure sensor 360 is provided at an outlet of valve 356 tomonitor a pressure PTGI at the proximal end of the insufflationcatheter. It is to be understood that pressure sensor 360 can beeliminated if not desired. An optional bacteria filter 362 is alsoprovided at the outlet of the TGI flow control system. Finally, ahousing 364 is provided to contain the elements of TGI flow controlsystem 320.

[0122] A second embodiment of a TGI flow control system 320′ accordingto the principles of the present invention is shown in FIGS. 19 and 20,where FIG. 20 is a flow schematic for the TGI flow control scheme ofFIG. 19. In this flow control technique, which is referred to as flowfeedback control (FFC), the exhaust flow from the patient circuit iscontrolled by means of an active control feedback loop, rather than thethrough the use of a valve with a constant flow rate, such as valve 80or 326. Thus, in this embodiment valve 326 is eliminated.

[0123] TGI flow control system 320′ includes a single TGI/Vent valve 370connected between the source of insufflation gas (an output 371 ofneedle valve 350), patient circuit via outlet line 324 and line 374, andinsufflation catheter 322 via outlet line 330. Valve 370 is a three-wayvalve moveable between two positions. In a first “enabled” or TGIposition, valve 370 communicates line 371 with line 330 so that the flowof insufflation gas is provided to the insufflation catheter. In thisconfiguration, line 371 and line 330 are disconnected from line 374. Ina second “disabled” or vent position, valve 370 communicates line 330with line 374 so that the insufflation catheter is connected to theambient atmosphere. In this configuration, line 371 is disconnected fromlines 330 and 374.

[0124] In the FFC system 320′, the constant exhaust flow that wasotherwise provided by valve 326 is provided by a simple servo-controlledsolenoid valve 380 and a flow meter 382. Valve 380 communicates the flowof gas from line 371 to ambient atmosphere. In a presently preferredembodiment, valve 380 is actively controlled based on the monitored flowvia flow sensor 382 to provide a flow of exhaust gas from 0 to 15 litersper minute (Ipm). Valve 380 is controlled so that the flow of exhaustgas substantially matches the flow insufflation gas so that there is nonet increase in the volume of gas in the overall ventilation/TGI systemover a respiratory cycle.

[0125] Valve 380 can be a bank of ON/OFF solenoid valves, an analog ordigital (step motor) servo valve, a voice-coil valve, or any other valvethat allows the flow rate to be controlled. In such a system, line 371provides a pathway for gas from the exhalation limb of the patientcircuit to valve 380 and flow meter 382. Valve 380 and 382 can beprovided as separate elements of can be integrated into a single unit.

[0126] In this system, the patient circuit pressure provides the drivepressure across the valve 380. Thus, a minimum patient circuit pressuremust be specified in order to use such a configuration. The system mustbe able to accommodate the saturated conditions of the gas. This couldinclude removal of water from the gas prior to entry into valve 380and/or flow meter 382, heating of measurement and control contactsurfaces, or heating of the gas prior to entry into the measurement andcontrol contact surfaces. A bacteria filter 384 is provided in line 324.In addition, a filter 386 is provided in the input line of the TGI flowcontrol system.

[0127] It should be noted that the FFC system eliminates the need for abypass flow control mode, because this system retains control of gasflow both into the and out of the patient circuit via valve 380.Nevertheless, a bypass mode can be provided by preventing a flow ofinsufflation gas from entering the insufflation catheter and preventinga flow of insufflation gas from entering the patient circuit.

[0128] The following table summarizes the position for main shutoffvalve 344, TGI/Vent valve 370, and servo-controlled valve 380. It shouldbe noted that in an enabled position, gas is allowed to flow in acontrollable manner from line 374 to ambient atmosphere through valve380 and in a disabled position the flow to ambient atmosphere throughvalve 380 is blocked. Shutoff TGI/Vent Exhaust Valve 344 Valve 370 Valve380 TGI Mode Enabled Enabled Enabled Bypass (1) Mode Enabled DisabledDisabled Bypass (2) Mode Disabled Enabled Disabled Vent Mode DisabledDisabled Disabled

[0129] A further embodiment of the present invention contemplates usinga roller pump in place of servo valve 380. Because a roller pump is apositive displacement device, volume flow is controlled simply bycontrolling the speed of the roller pump. Thus, a flow meter is notnecessary because flow control could be executed via the pump motorspeed. In a configuration with a roller pump, a tube that is connectedto the patient circuit exhalation limb is wound around the inside of thepump mandrel. As the pump rollers rotate and compress the tubing, agiven volume of gas is displaced from the patient circuit. An additionaladvantage to such a system is that there is no requirement for drivepressure from the patient circuit (i.e., no minimum patient circuitpressure).

[0130]FIG. 21 is a schematic diagram of a third embodiment of a TGI flowcontrol system 320″ according to the principles of the presentinvention. This embodiment is similar to that shown in FIG. 20, exceptthat the main shutoff valve has been eliminated. The following tablesummarizes the position for TGI/Vent valve 370 and servo-controlledvalve 380. TGI/Vent Valve 370 Exhaust Valve 380 TGI Mode Enabled EnabledBypass Mode Disabled Disabled Vent Mode Disabled Disabled

[0131] In the embodiments discussed above, the ventilation system andthe TGI system are shown as separate systems. However, the presentinvention also contemplates that these two systems can be incorporatedinto a single, integrated system. FIG. 22 is a schematic diagram of afirst embodiment of a ventilator/TGI system combination 400 according tothe principles of the present invention.

[0132] Ventilator/TGI system 400 includes a patient ventilation system402 that generates a flow of gas for delivery to an airway of a patient.A patient circuit 404 is coupled to ventilation system 402 for carryingthe flow of gas from the ventilation system to an airway of a patient.An insufflation system 406 provides a flow of insufflation gas fordelivery to the patient's airway. An insufflation catheter 408 iscoupled to the insufflation system for carrying the flow of gas from theinsufflation system to an airway of a patient. A portion of theinsufflation system is disposed within the patient circuit. A housing410 contains both the patient ventilation system and the insufflationsystem.

[0133] The source of gas for the insufflation system and the ventilationsystem can be separate from one another. For example, in the previousembodiments, a pressure generator, such as a blower, piston, or bellows,creates the flow of gas for the ventilation system, and tanks ofpressurized oxygen and air provide the insufflation gas. It is to beunderstood that these two sources of gas can be provided from a commonsource. For example, FIG. 23 illustrates a schematic diagram of a secondembodiment of a ventilator/TGI system 420 combination according to theprinciples of the present invention. In this embodiment, a commonpressure generator 422 generates a flow of pressurized gas for use by aTGI system 424 and a ventilation system 426. It is to be understood thata source of oxygen should be provided to the TGI system so that the flowof insufflation gas has an FIO₂ above that of air. The source of oxygencan be a tank of oxygen, an oxygen concentrator, a supply of liquidoxygen, or any other source of oxygen. It should also be understood thatthe supplemental oxygen can also be provided to the ventilation system,as is known in the art.

[0134] Referring again to FIG. 23, a first tube 430 is disposed in ahousing 432 that connects an outlet of pressure generator 422 to apatient circuit connector 434. A second tube 436 also disposed in thehousing connects a source of insufflation gas 422 to an insufflationcatheter connector 438. A flow control system, which in the illustratedembodiment is ventilation system 426, is coupled to first tube 430 tocontrol a flow of gas in a patient circuit 440 coupled to patientcircuit connector 434. Another flow control system is coupled to secondtube 436 to control a flow of insufflation gas to an insufflationcatheter 442 coupled to insufflation catheter connector 438.

[0135] The present invention also contemplates providing the TGI flowcontrol system discussed above with respect to FIGS. 17-21 inconjunction with the TGI/ventilation combined system. For example, thepresent invention contemplates providing one or move valves coupledbetween the first tube, the second tube, and the source of insufflationgas to control a flow of gas between the patient circuit, theinsufflation catheter, and the source of insufflation gas as discussedabove.

[0136] Pressure sensor 360 can be used to monitor the pressure at thelungs of the patient because the distal end portion of the insufflationcatheter is disposed in the patient's lungs. The pressure PTGI measuredat the proximal end of the insufflation catheter can be used todetermine the pressure at the lungs if the pressure drop along theinsufflation catheter is compensated. Of course, other environmentalconditions and the dynamic compliance of the system should also be takeninto consideration in order for the pressure measured by pressure sensor360 to be an accurate determination of the pressure in the patient'slungs. This feature of the present invention allows pressure sensor 360to be used to monitor the pressure in the patient's lungs. For example,it is important that the lung pressure does not exceed predeterminedlimits, which include a high pressure limit and a low pressure limit.Pressure sensor 360 can be used to monitor this pressure and providealarms or shutoff decisions if the monitored pressure exceedspredetermined limits.

[0137] The present invention also contemplates controlling the FIO₂ ofthe gas provided by the ventilation system and/or controlling the FIO₂of the gas provided by the TGI system so that the FIO₂ values of thesegas flows are substantially the same. Matching the FIO₂ of the gasprovided by the ventilation system and the FIO₂ of the gas provided bythe TGI system can be accomplished manually, for example by having theuser set the FIO₂ of the gas provided by the TGI system to match that ofthe ventilation system or vice versa.

[0138] Matching the FIO₂ of the gas provided by the ventilation systemand the FIO₂ of the gas provided by the TGI system can also beaccomplished automatically. For example, by monitoring the FIO₂ of thegas provided by the ventilation system using any conventional oxygenconcentration monitoring system and automatically controlling the FIO₂of the gas provided by the TGI system to match that of the ventilationsystem or vice versa. The FIO₂ matching between the TGI system and theventilation system can also be provided by providing both systems withgas from the same source, i.e., having the same FIO₂.

[0139] A further embodiment of the present invention contemplatesactively controlling the operation of the heated humidifier based on themonitored conditions of the ventilation system, the TGI system, or both.More specifically, the present invention contemplates causing the TGIflow control system to shut off the heat to the humidifier automaticallyif an alarm condition for the ventilation system, the TGI system, orboth is detected. Typical alarm conditions that should cause the heat tobe discontinued includes: high pressure, low pressure, and power supplyerrors. The present invention also contemplates decreasing or shuttingoff the heat to the heated humidifier when the flow of insufflation gasto the insufflation catheter is reduced or stopped. For example, if theinsufflation flow is stopped so that a caregiver can suction thepatient, the heat to the humidifier is also stopped. This preventsheating of the gas within the humidifier so that the patient does notreceive a bolus of over-heated gas when the flow of insufflation gas tothe insulation catheter resumes.

[0140] The present invention contemplates that the various components ofthe insufflation system of the present invention be made from any of anumber of materials, so long as such materials are of sufficientstrength and durability to function for their intended purpose. It isfurther desirable that, whenever necessary, the materials used for thevarious components of the present invention be compatible for use inmedical applications.

[0141] Although the invention has been described in detail for thepurpose of illustration based on what is currently considered to be themost practical and preferred embodiments, it is to be understood thatsuch detail is solely for that purpose and that the invention is notlimited to the disclosed embodiments, but on the contrary, is intendedto cover modifications and equivalent arrangements that are within thespirit and scope of the appended claims.

What is claimed is:
 1. A tracheal gas insulation system comprising: a patient circuit adapted to couple a ventilator to an airway of a patient; an insufflation catheter having a proximal end portion located generally outside a patient and a distal end portion adapted to be located in an airway of a patient for providing a flow of insulation gas to such a patient; a source of insulation gas; and a flow control system coupled between the patient circuit, the insufflation catheter, and the source of insufflation gas so as to control a flow of gas between the patient circuit, the insufflation catheter, and the source of insufflation gas.
 2. The system of claim 1, wherein the flow control system includes a first selectively actuatable valve connected between the source of insufflation gas, the insulation catheter, and the patient circuit, wherein the first valve is adapted to be arranged to: a) communicate the insufflation catheter with the source of insufflation gas and disconnect the patient circuit from the source of insufflation gas and the insufflation catheter in a first configuration, b) communicate the insufflation catheter with the patient circuit and disconnect the source of insufflation gas from the insulation catheter and the patient circuit in a second configuration.
 3. The system of claim 2, wherein the flow control system includes a servo-controlled valve adapted to control a flow of gas from the patient circuit to ambient atmosphere.
 4. The system of claim 3, wherein the flow control system includes a flow sensor adapted to measure a flow of gas through the servo-controlled valve.
 5. The system of claim 2, further comprising a master shut-off valve adapted to disconnect the source of insufflation gas from the insufflation catheter and the patient circuit.
 6. The system of claim 1, further comprising a pressure sensor adapted to determine a pressure in the insufflation catheter.
 7. The system of claim 1, wherein the flow control system includes a first selectively actuatable valve connected between the source of insufflation gas, the insufflation catheter, and the patient circuit, wherein the first valve is adapted to be arranged to: a) communicate the insufflation catheter with the source of insufflation gas and disconnect the patient circuit from the source of insufflation gas in a first configuration, (TGI) b) communicate the source of insufflation gas with the patient circuit and disconnect the insufflation catheter from the patient circuit and the source of insufflation gas in a second configuration. (VENT)
 8. The system of claim 7, further comprising a second selectively actuatable valve connected between the insufflation catheter and the patient circuit, wherein the second valve is adapted to communicate the insufflation catheter and the patient circuit responsive to the first valve being in the second configuration.
 9. The system of claim 7, further comprising a master shut-off valve adapted to disconnect the source of insufflation gas from the insufflation catheter and the patient circuit.
 10. A method of providing an insufflation gas to a patient comprising: providing a patient circuit adapted to couple a ventilator to an airway of a patient; providing an insufflation catheter having a proximal end portion located generally outside a patient and a distal end portion adapted to be located in an airway of a patient for providing a flow of insufflation gas to such a patient; providing a source of insufflation gas; and controlling a flow of gas between the patient circuit, the insufflation catheter, and the source of insufflation gas.
 11. The method of claim 10, wherein controlling the flow of gas between the patient circuit, the insufflation catheter, and the source of insufflation gas includes: a) communicating the insufflation catheter with the source of insufflation gas and disconnecting the patient circuit from the source of insufflation gas and the insufflation catheter in a first configuration, (TGI) b) communicating the insufflation catheter with the patient circuit and disconnecting the source of insufflation gas from the insufflation catheter and the patient circuit in a second configuration. (VENT)
 12. The method of claim 11, further comprising controlling a flow of gas from the patient circuit to ambient atmosphere.
 13. The method of claim 12, further comprising measuring a flow of gas through from the patient circuit to the ambient atmosphere.
 14. The method of claim 11, further comprising disconnecting the source of insufflation gas from the insufflation catheter and the patient circuit via a master shut-off valve.
 15. The method of claim 10, further comprising measuring a pressure in the insufflation catheter.
 16. A ventilator and tracheal gas insufflation system comprising: a housing; a pressure generator disposed within the housing; a patient circuit connector disposed on an exterior of the housing adapted to connect to a patient circuit; an insufflation catheter connector disposed on the exterior of the housing adapted to connect to an insufflation catheter; a first tube disposed in the housing and connecting an outlet of the pressure generator to the patient circuit connector; a second tube disposed in the housing and connecting a source of insufflation gas to the insufflation catheter connector; and a first flow control system operatively coupled to the first tube to control a flow of gas in the patient circuit; and a second flow control system operatively coupled to the second tube to control a flow of insufflation gas in the insufflation catheter.
 17. The system of claim 16, wherein the second flow control system is coupled between the first tube, the second tube, and such a source of insufflation gas so as to control a flow of gas between the patient circuit, the insufflation catheter, and the source of insufflation gas.
 18. The system of claim 16, wherein the source of insufflation gas is the pressure generator.
 19. The system of claim 16, further comprising: an insufflation catheter connected to the insufflation catheter connector; and a patient circuit connected to the patient circuit connector.
 20. The system of claim 16, further comprising a sensor operatively coupled to the second tube to detect a characteristic associated with the flow of gas in the second tube.
 21. A ventilator and tracheal gas insufflation system comprising: a patient ventilation system adapted to generate a flow of gas for delivery to an airway of a patient; a patient circuit operatively coupled to the ventilation system for carrying the flow of gas from the ventilation system to an airway of a patient; an insufflation system adapted to generate a flow of insufflation gas for delivery to an airway of such a patient; an insufflation catheter operatively coupled to the insufflation system for carrying the flow of gas from the insufflation system to an airway of a patient, wherein a portion of the insufflation system is disposed within the patient circuit; and a housing containing the patient ventilation system and the insufflation system.
 22. The system of claim 21, further comprising: a patient circuit connector disposed on the housing and adapted to connect the patient circuit to the ventilation system; and an insufflation catheter connector disposed on the housing and adapted to connect the insufflation catheter to the insufflation system.
 23. The system of claim 21, wherein the ventilation system and the insufflation system share a common source of gas. 